Electronic Structure of Nonionic Surfactant-Modified PEDOT:PSS and Its Application in Perovskite Solar Cells with Reduced Interface Recombination.

ABSTRACT

The interfacial properties of organolead halide perovskite solar cells (PSCs) affect the exciton and charge-transport dynamics significantly. Thus, proper modification of the interfaces between perovskite and charge-transport layers is an efficient method to increase the power conversion efficiency (PCE) of PSCs. In this work, we explore the effect of a nonionic surfactant, that is, Triton X-100 (TX) additive, in the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOTPSS) hole-transport layer. The electronic structure of TX-modified PEDOTPSS is investigated with ultraviolet/X-ray photoelectron spectroscopy and X-ray absorption spectroscopy with various TX concentrations. The surface of the TX-modified PEDOTPSS layer showed high TX content, and thus the semimetallic properties of PEDOTPSS were suppressed conspicuously by its insulating nature. With the TX-modified PEDOTPSS, the PCE of methylammonium lead iodide (MAPbI3) PSCs increased significantly. To elucidate the origin of the improved device performance, the electrical properties and photoluminescence were investigated comprehensively. Consequently, it was found that the TX additive inhibits interface recombination between PEDOTPSS and MAPbI3, which is caused by the suppression of semimetallic properties of the PEDOTPSS surface. Hence, we fabricated flexible PSCs successfully using a graphene electrode and TX-modified PEDOTPSS.